Not only can downloaders choose the amount they want to pay, they can also decide whether they want the money to go to the developers, charity or any combination of both. The minimum amount required to get a download link is a penny.
Thus far the project has been a great success. The games have been downloaded more than 80,000 times and have raised $683,090 at the time of writing. Linux users have been the most generous with an average donation of $14.01, while Windows users are stuck at $7.31.

Very interesting that even though all you have to pay is a penny, there are still a lot of people pirating the software. Also it is very cool how well this model is working for them.